Biochemistry of apple aroma: A review

Abstract

SummaryFlavour is a key quality att ribute of apples defi ned by volatile aroma compounds. Biosynthesis of aroma compounds involves metabolic pathways in which the main precursors are fatt y and amino acids, and the main products are aldehydes, alcohols and esters. Some enzymes are crucial in the production of volatile compounds, such as lipoxygenase, alcohol dehydrogenase, and alcohol acyltransferase. Composition and concentration of volatiles in apples may be altered by pre-and postharvest factors that cause a decline in apple fl avour. Addition of biosynthetic precursors of volatile compounds may be a strategy to promote aroma production in apples. The present manuscript compiles information regarding the biosynthesis of volatile aroma compounds, including metabolic pathways, enzymes and substrates involved, factors that may aff ect their production and also includes a wide number of studies focused on the addition of biosynthetic precursors in their production.

Characterization of aroma-active compounds in delicious apples juices by gas chromatography-mass spectrometry (GC-MS), gas chromatography–olfactometry (GC-O) and odor activity value (OAV)

“…Among those compounds, benzaldehyde (6.568-18.508 mg/kg), 2-methylbutanol (2.301-13.421 mg/kg), butanol (0.643-5.247 mg/kg), (E) -2-hexenal (2.050-9.804 mg/kg), ethyl butanoate (1.914-6.906 mg/kg), ethyl 2-methylbutanoate (1.419-6.867 mg/kg) presented relatively higher amounts than other compounds. The results were agreed with other studies which found that esters, alcohols, aldehydes, ketones compounds could be considered as the main compounds to delicious apple (Espinodíaz et al, 2016). The OAV was considered as useful method to evaluate the contribution of aroma compound to whole aroma.…”

Analysis of volatile compounds as quality indicators for Fuji apples after cold storage

“…As listed in Table , 3 alcohols, 28 esters, and 2 terpenes were tentatively identified. Esters are generated by the esterification of alcohols and acyl‐CoA, and acyl alcohol transferase (AAT) is the key enzyme that transfers an acyl group to an alcohol (Bartley, Stoker, Martin, Hatfield, & Knee, ; Espino‐Díaz, Sepúlveda, González‐Aguilar, & Olivas, ). However, independent to the reaction of alcohols and esters, terpenoids including α‐farnesene and d ‐limonene are generated via mevalonate and deoxyxylulose phosphate pathways (Eisenreich, Bacher, Arigoni, & Rohdich, ; Sanz & Perez, ).…”

“…The type of esters generated from apples is dependent on the specificity of AAT enzyme to alcohols and acyl‐CoA (Echeverrıa, Graell, et al, ). Apples have AAT enzymes with various substrate‐specificity depending on their variety (Espino‐Díaz et al, ). It has been reported that exogenous HeOH and 2mBuOH in Fuji apples are converted to hexyl and 2‐methylbutyl acetate, respectively (Holland et al, ).…”

Volatile Changes during Storage of Shelf Stable Apple Juice: Integrating GC-MS Fingerprinting and Chemometrics

“…Hundreds of volatile compounds have been detected in the aroma profile of apples. These compounds are categorized as esters, alcohols, aldehydes, ketones and ethers [1,2]. Some of these compounds are labeled as "character impact," including trans-2-hexenal (green), hexanal (grassy, green), butyl acetate (red apple aroma), ethyl butanoate (fruity), butan-1-ol (sweet aroma), etc.…”